Alternate Definitions

Tangible (such as human resources) or intangible (such a brand, knowledge, skills) asset that (unlike the hard assets such as cash, equipment, land) is not normally included in a firm's financial statements. - BusinessDictionary.Com

Soft Assets in the council environment seems to apply more to the non-infrastructure (hard) assets found in the Parks and Gardens area of Councils, like;

Gardens

Trees

Reserves

Walking tracks

Sports field surfaces

etc

where normal asset management principles and particularly the standard calculation of "sustainability" do not apply.

Soft assets like those mentioned above, are generally ignored (or consolidated) in council asset management plans, which under-values their importance.
A separate approach to managing "soft" assets is required. The focus with these assets needs to be on the service level they provide now and into the future.